1. Field of the Invention
The present invention relates to a multi-air conditioning system, and more particularly, to an air conditioning system having an improved refrigerant circulation structure capable of smoothly feeding back a refrigerant that circulates in a refrigerant circulation system.
2. Description of the Background Art
FIG. 1 is a construction view showing an air conditioning system in accordance with the conventional art.
As shown, the conventional air conditioning system comprises an indoor unit 111 for introducing a first refrigerant, a first tank (suction tank) 121 connected to an outlet side refrigerant line 111b of the indoor unit 111 for sucking a first refrigerant, a second tank (discharge tank) 141 disposed to be lower than the suction tank 121 and connected to an inlet side refrigerant line 111a of the indoor unit 111 for discharging a first refrigerant to the indoor unit 111, a middle tank 131 installed between the suction tank 121 and the discharge tank 141 for feeding back the first refrigerant stored in the suction tank 121 to the discharge tank 141, and a heat source cycle 150 for depressurizing and cooling the first refrigerant of the suction tank 121 by circulating a second refrigerant, and heating the first refrigerant of the discharge tank 141.
The discharge tank 141 is positioned to be lower than the middle tank 131, and the middle tank 131 is positioned to be lower than the suction tank 121. That is, the suction tank 121, the middle tank 131, and the discharge tank 141 are sequentially positioned.
A first connection line 125 for connecting a lower portion of the suction tank 121 to a lower portion of the middle tank 131 is installed between the suction tank 121 and the middle tank 131. A switching valve 137 is installed at the first connection line 125.
A first pressure equalizing line 123 for connecting a lower portion of the suction tank 121 to an upper portion of the middle tank 131 is installed between the suction tank 121 and the middle tank 131. The switching valve 137 is installed at the first pressure equalizing line 123.
A second connection line 135 for connecting a lower portion of the middle tank 131 to a lower portion of the discharge tank 141 is installed between the middle tank 131 and the discharge tank 141. The switching valve 137 is installed at the second connection line 135.
A second pressure equalizing line 133 for connecting an upper portion of the middle tank 131 to an upper portion of the discharge tank 141 is installed between the middle tank 131 and the discharge tank 141. The switching valve 137 is installed at the second pressure equalizing line 133.
The heat source cycle 150 comprises a compressor 151 for compressing a second refrigerant, a condenser 153 connected to an outlet side refrigerant line 151a of the compressor 151 and heat-exchanging with a first refrigerant inside the discharge tank 141, an evaporator 155 connected to an inlet side refrigerant line 151b of the compressor 151 and heat-exchanging with a first refrigerant inside the suction tank 121, and an outdoor expansion valve 157 installed at an outlet side refrigerant line 153a of the condenser 153.
In the conventional air conditioning system, in case of the heat source cycle 150, a second refrigerant provided from the compressor 151 passes through the condenser 153, the outdoor expansion valve 157, and the evaporator 155, and then is returned to the compressor 151, which is repeated.
In case of a heat driving system 110, a first refrigerant supplied from the discharge tank 141 passes through the indoor unit 111, and then is fed back to the suction tank 121, the middle tank 131, and the discharge tank 141, which is repeated.
The first refrigerant inside the discharge tank 141 is heat-exchanged by the condenser 153 thus to be introduced into the indoor unit 111. Then, the first refrigerant introduced into the indoor unit 111 is heat-exchanged via an indoor expansion valve 115 and an indoor heat exchanger 113, thereby heating or cooling an indoor room.
The first refrigerant having passed through the indoor unit 111 is introduced into the suction tank 121, and then is heat-exchanged by the evaporator 155 thus to be condensed. When the first refrigerant having an amount more than a certain degree is stored in the suction tank 121, a controller (not shown) controls each switching valve 137 of the first pressure equalizing line 123 and the first connection line 125. Accordingly, the first refrigerant stored in the suction tank 121 is fed back to the middle tank 131 by a height difference between the suction tank 121 and the middle tank 131 and by a gravitation.
Next, the controller controls each switching valve 137 of the second pressure equalizing line 133 and the second connection line 135 in the same manner as the aforementioned manner. Accordingly, the first refrigerant stored in the middle tank 131 is fed back to the discharge tank 141.
However, in the conventional air conditioning system, the first liquid refrigerant is fed back by a height difference among the suction tank, the middle tank, and the discharge tank and by gravitation. Accordingly, an entire volume of the air conditioning system is increased and an entire height of the air conditioning system is increased, thereby having a limitation in installing the air conditioning system and increasing a fabrication cost. Furthermore, the first refrigerant more than a certain amount has to be stored in the suction tank and the discharge tank.